Ester oils

ABSTRACT

According to a first aspect, an ester oil, in particular for producing a hydraulic fluid and/or a lubricant, containing an esterification product from the esterification of at least one monoalcohol with at least one polycarboxylic acid, is characterized in that the monoalcohol and/or the polycarboxylic acid originates from renewable raw materials. According to a second aspect, an ester oil, in particular for producing a hydraulic fluid and/or a lubricant, containing an esterification product from the esterificati-on of at least one monocarboxylic acid with at least one dialcohol, is characterized in that the dialcohol and/or the monocarboxylic acid originates from renewable raw materials.

TECHNICAL FIELD

The invention relates to ester oil, especially for production of ahydraulic oil and/or of a lubricant, comprising an esterificationproduct of at least one monoalcohol with at least one polycarboxylicacid. The invention further relates to an ester oil, especially forproduction of a hydraulic oil and/or of a lubricant, comprising anesterification product of at least one monocarboxylic acid with at leastone dialcohol. The invention additionally relates to processes forpreparing ester oils and to the use of ester oils.

STATE OF THE ART

Lubricants serve particularly to reduce friction and wear, to preventcorrosion, for sealing, for cooling, and to damp vibration or transmitforce in mechanical systems. According to the application envisaged,lubricants are used in the solid, liquid or gaseous state.

Liquid lubricants in particular are widespread in a wide variety ofdifferent technical fields and are used, inter alia, as motor oils,turbine oils, hydraulic fluids or transmission oils.

A known class of liquid lubricant oils is that of ester-based lubricantoils, which comprise organic reaction products of carboxylic acids withalcohols as the main component. The demands on modern ester oils arevaried. An ester oil has to meet the demands defined by the envisageduse, for example in terms of density, viscosity, viscosity index,solidification point, pour point, flashpoint, seal compatibility, agingresistance, toxicity and/or biodegradability.

DE 10 2006 001 768 (Cognis) describes, for example, esters based onbranched Guerbet alcohols as lubricant and carrier medium for hydraulicfluids. The esters with branched alcohols can also be prepared fromrenewable raw materials.

DE 10 2004 034 202 (SASOL) provides ester mixtures, for example ashydraulic oils, consisting of the reaction product of a branched alcoholwith a polycarboxylic acid. Branched alcohols mentioned are especially2-alkyl-branched alcohols, preferably Guerbet alcohols. However, thereis no mention of renewable raw materials.

DE 10 2006 027 602 (Cognis) describes lubricants, for exampletransmission, industrial and motor oils, and hydraulic oils. The baseoils are present here as mixtures of hydrocarbons (mineral oil, PAOs)with high-viscosity esters (HVE), which additionally have additives toimprove the viscosity index. Reaction products of carboxylic acids andalcohols are disclosed here. However, these do not originate fromrenewable raw materials.

However, the preparation of known esters is comparatively complex, andthey are correspondingly comparatively uneconomic.

Even though ester oils per se have long been known, the economic andenvironmentally friendly preparation of optimized and flexibly usableester oils is still a great challenge.

DESCRIPTION OF THE INVENTION

It is an object of the invention to provide an ester oil which belongsto the technical field mentioned at the outset, is producible in a veryinexpensive and environmentally friendly manner, and especially hasideal properties for use as a lubricant oil.

A first solution to the problem is defined by the features of claims 1and 41.

A first aspect of the invention relates to ester oil, especially forproduction of a hydraulic oil and/or lubricant, comprising anesterification product of at least one monoalcohol with at least onepolycarboxylic acid, wherein the monoalcohol and/or the polycarboxylicacid originate from renewable raw materials.

In a process for preparing such an ester oil, especially for use in ahydraulic oil and/or a lubricant, a monoalcohol is reacted with apolycarboxylic acid to give an ester oil, the monoalcohol and/or thepolycarboxylic acid originating from renewable raw materials.

In principle, the monoalcohol and/or the polycarboxylic acid may alsooriginate from mixtures of renewable and fossil raw materials. It isthus not obligatory that the monoalcohol and/or the polycarboxylic acidoriginate exclusively from renewable raw materials. In a preferredvariant, however, the monoalcohol and/or the polycarboxylic acidoriginate essentially exclusively from renewable raw materials.

A renewable raw material in this context is understood especially tomean an organic compound which is obtained by direct isolation and/or byupgrading from organic raw materials, the organic raw materials beingdrawn principally from the natural world. Useful organic raw materialsinclude, for example, plants. Renewable raw materials should not beconfused with non-renewable raw materials from fossil sources. Thelatter are, for example, degradation products from dead plants and/oranimals, the formation of which takes place in geological orastronomical periods, i.e. began well before 60 000 years.

Renewable raw materials can be distinguished from non-renewable rawmaterials from fossil sources particularly through the proportion of theradioactive ¹⁴C carbon isotope in the raw material. Raw materials fromfossil sources, owing to their age, have essentially no ¹⁴C carbonisotopes, whereas a characteristic proportion of the ¹⁴C carbon isotopeis present in renewable raw materials. ¹⁴C carbon isotopes are formedconstantly by nuclear reactions in the upper atmosphere of the earth,and get into the biosphere via the carbon cycle. There is essentially anequilibrium between new formation and constant radioactive decay.Accordingly, in living organisms in the biosphere (plants, animals),about the same distribution ratio of radioactive carbon (¹⁴C) tonon-radioactive carbon (¹²C and ¹³C) is established as is also presentin the atmosphere. The inventive ester oils, based on the carboncontent, are formed from renewable raw materials preferably to an extentof at least 25 mol %, further preferably at least 50 mol %, even furtherpreferably at least 60 mol %, especially preferably at least 70 mol %.Lubricants having a minimum proportion of 25 mol % of the totalformulation from renewable raw materials (RRM) are referred to in Europeas biolubes. Further ecolabels are applied to lubricants when theyconsist of renewable raw materials, based on the carbon content,preferably at least 50 mol %, even further preferably at least 60 mol %,especially preferably at least 70 mol %. In both cases, criteriarelating to toxicology also have to be met. In other regions, othercriteria have to be observed. For instance, the designation“biopreferred” known in the USA requires particular proportions fromrenewable raw materials, but no statements are made regarding toxicity.

The radiocarbon method used to determine the proportion of ¹⁴C carbonisotopes is very familiar to the person skilled in the art (ASTM D6866or DIN EN 15440). The chemically prepared samples are analyzed, forexample, by the Libby counting tube method, by liquid scintillationspectrometry and/or by mass spectrometry detection in accelerators.These can also take into account the short- and long-term variations inthe production of the ¹⁴C carbon isotopes over the course of periods inthe history of the earth.

A particularly suitable and standardized process for determining theproportion of renewable raw materials in a product to be tested isdefined, for example, in the standard ASTM D6866-08. This determines theorganic content of the product originating from renewable raw materialsin relation to the total organic content of the product. Inorganiccarbon and substances with no carbon content are not included. Theprocess is based on liquid scintillation spectroscopy. The measuredratio of ¹⁴C to ¹²C in the product to be tested is determined relativeto a standard compound (oxalic acid).

The term “lubricant” is understood to mean particularly an intermediatesubstance which serves for reduction of friction and wear, and for forcetransmission, cooling, vibration damping, sealing and/or for corrosionprotection. More particularly, the lubricant of interest in this contextis a fluid.

A specific lubricant is, for example, a hydraulic fluid. A hydraulicfluid is especially a fluid usable for transfer of energy (volume flow,pressure) in a hydraulic system. The hydraulic liquid is preferably ahydraulic oil, which is especially water-immiscible.

As has been found, the inventive ester oils are particularlyadvantageous according to the first aspect, in which the monoalcoholand/or the polycarboxylic acid originate from renewable raw materials.Firstly, such ester oils have advantageous properties with regard to useas lubricants and hydraulic oils. More particularly, such ester oilssimultaneously have good lubricant properties and a high air separationcapacity. It has likewise been found that the ester oils have a highlifetime or aging resistance compared to known lubricant oils.

In addition, the inventive ester oils have a high flashpoint, such thatuse at relatively high oil sump and component temperatures is possiblewithout risk. In addition, the pour point of the ester oils isrelatively low, as a result of which the esters are also usable at lowtemperatures. For a liquid product, the pour point denotes thetemperature at which it is still just free-flowing in the course ofcooling. Thus, the inventive ester oils can be used within a broadtemperature range.

The viscosity of the inventive ester oils is additionally within anideal range for lubricant oils and hydraulic fluids. There is thus norequirement for adjustment of the viscosity by mixing with another, forexample thicker, oil. It is thus also possible to use the inventiveester oils at elevated temperatures without occurrence of changes inviscosity in the ester oil, as is the case for mixed oils owing to thedifferent vaporization properties of the individual oil components.

There is also no requirement for a usually disadvantageous addition ofviscosity-modifying thickeners in the inventive ester oils, owing to therelatively high viscosity. The air separation capacity of the ester oilsis thus not impaired and the problem of softening of seals, for examplein hydraulic systems, barely occurs with the inventive ester oils.

Moreover, the viscosity index (VI), which characterizes the temperaturedependence of the kinematic viscosity of a lubricant oil, is relativelyhigh in the inventive ester oils. The ester oils therefore exhibit arelatively small temperature-dependent change in viscosity, which isvery advantageous for most practical applications, since they are usablewith relatively constant properties within a broad temperature range.

As has been found, the vaporization losses (NOACK) of the inventiveester oils are also relatively low.

Furthermore, the use of renewable raw materials enables particularlyenvironmentally friendly and economic production. Especially through theuse of renewable raw materials, the inventive ester oils aresimultaneously also convincing in terms of toxicology andbiodegradability. The inventive ester oils essentially all haverelatively rapid and easy biodegradability.

The combination of the inventive chemical structure and the use ofrenewable raw materials thus enables unexpectedly economic preparationof ester oils which have surprisingly advantageous properties aslubricants.

Advantageously, the polycarboxylic acid originates from renewable rawmaterials. This has been found to be advantageous especially with regardto the economic viability of the preparation. More particularly, thepolycarboxylic acid is producible from vegetable oils, which are alreadyavailable globally in large volumes. It is additionally possible toobtain a multitude of different polycarboxylic acids from renewable rawmaterials or vegetable oils in relatively simple chemical process steps.Moreover, compliance with current environmental regulations or ecolabelsis enabled.

However, it is also possible in principle to use, for example,polycarboxylic acid synthesized from fossil raw materials, if thisappears to serve the purpose.

The polycarboxylic acid is preferably saturated. In other words, thereare preferably only single bonds between the carbon atoms of thepolycarboxylic acid. As has been found, ester oils with suchpolycarboxylic acids are especially more oxidation-resistant and stable,which is to the benefit of the lifetime or aging resistance of the esteroils.

Under some circumstances, however, mono- or polyunsaturatedpolycarboxylic acids can be used for specific purposes.

In a further preferred variant, the polycarboxylic acid is unbranched.In other words, the polycarboxylic acid preferably has an unbranchedcarbon chain, which is especially linear. This has been found to beadvantageous for a multitude of applications.

In another, likewise advantageous variant, the polycarboxylic acid,however, may also be branched. Whether an unbranched or branchedpolycarboxylic acid is more advantageous depends on factors includingthe monoalcohols used for the ester oil and the desired substanceproperties of the ester oil. The use of branched polycarboxylic acidscan under some circumstances lower the pour point and increase theflashpoint, which may be advantageous for specific applications. Inaddition, ester oils with branched polycarboxylic acids exhibit higherseal compatibilities under some circumstances. This aspect is addressedin more detail further down in the context of the monoalcohols.

The polycarboxylic acid preferably has 6-13 carbon atoms, especiallypreferably 8-13 carbon atoms. Such polycarboxylic acids can firstly beobtained economically from renewable raw materials, and secondly enablethe production of a wide range of ester oils which are particularlysuitable as lubricants or hydraulic oils.

In principle, however, it is also possible to provide polycarboxylicacids having fewer than 6 or more than 13 carbon atoms. According to thedesired properties of the ester oils, this may even be advantageous.

More preferably, the polycarboxylic acid comprises a dicarboxylic acid.Together with monoalcohols, it is thus possible to form dicarboxylicesters which are particularly suitable as lubricants and hydraulic oils.In addition, the production of dicarboxylic acids from renewable rawmaterials, for example vegetable oils, is possible without any problem,which is to the benefit of economic viability.

In principle, however, it is also possible to use other polycarboxylicacids, for example tricarboxylic acids.

Advantageously, the dicarboxylic acid comprises especially adipic acid(1,6-hexanedioic acid; HOOC—C₄H₈—COOH), suberic acid (octanedioic acid;HOOC—C₆H₁₂—COOH), azelaic acid (nonanedioic acid; HOOC—C₇H₁₄—COOH),sebacic acid (decanedioic acid; HOOC—C₈H₁₆—COOH), dodecanedioic acid(HOOC—C₁₀H₂₀—COOH) and/or brassylic acid (HOOC—C₁₁H₂₂—COOH). Theseunbranched dicarboxylic acids having 6, 8, 9, 10, 12 and 13 carbon atomscan be produced from renewable raw materials or vegetable oils. Inaddition, these dicarboxylic acids with a multitude of monoalcoholsobtainable from renewable raw materials can be used to prepare esteroils suitable for lubricants or hydraulic oils.

In principle, however, it is also conceivable to use polycarboxylicacids having three or even more carboxylic acid groups. It is alsopossible to use dicarboxylic acids other than the above representativeshaving, for example, fewer than 6 carbon atoms or more than 13 carbonatoms. For example, it is possible to use branched derivatives of adipicacid, suberic acid, azelaic acid, dodecanedioic acid and/or brassylicacid. These branched derivatives are especially methyl-branchedderivatives, for example trimethyladipic acid.

It may also be advantageous to provide a mixture of at least twodifferent polycarboxylic acids. In this case, it is firstly possible tocontrol the properties of the ester oils more precisely, and it issecondly possible to further optimize the preparation process with aview to economic viability. Advantageously, the at least two differentpolycarboxylic acids originate from renewable raw materials.

In a further optional variant, the polycarboxylic acid is a cyclicpolycarboxylic acid, especially a cyclic dicarboxylic acid, morepreferably 1,2-cyclohexanedicarboxylic acid [CAS #: 2305-32-0; C₈H₁₂O₄;M_(w)=172.2] and/or 1,4-cyclohexanedicarboxylic acid [CAS #: 619-82-9;C₈H₁₂O₄; M_(w)=172.2].

In particular, the at least one monoalcohol originates from renewableraw materials. The inventive ester oils can thus be preparedparticularly economically via fatty acids from vegetable oils. Amultitude of different monoalcohols can be obtained from fatty acids byoleochemical means by chemical reactions known per se. Since at leasttwo moles of monoalcohol can be converted in each case per mole ofpolycarboxylic acid, the use of monoalcohols from renewable rawmaterials additionally makes it possible to achieve a relatively highproportion of renewable raw materials in the reaction product or theester oil. Thus, compliance with current environmental regulations orecolabels is also simplified.

More preferably, both the polycarboxylic acid and the monoalcoholsoriginate from renewable raw materials. It is thus possible to furtherimprove the aforementioned advantages.

However, it is also possible in principle to use monoalcohols fromfossil raw materials, if this appears appropriate to the purpose.

The at least one monoalcohol is preferably saturated. In other words,preferably only single bonds are present between the carbon atoms of theat least one monoalcohol. It is thus possible to improve particularlythe oxidation resistance and stability of the ester oil.

In a particularly advantageous variant, both the polycarboxylic acid andthe at least one monoalcohol are saturated. It is thus possible togreatly improve the oxidation and aging resistance.

In principle, the at least one monoalcohol, however, may also be mono-or polyunsaturated.

Advantageously, the at least one monoalcohol is unbranched. Thus, the atleast one monoalcohol advantageously has an unbranched carbon chain,which is especially linear. The monoalcohol in this case is alsoreferred to as an n-monoalcohol. This has been found to be advantageousfor a multitude of applications. This is the case especially for acombination with unbranched polycarboxylic acids and particularly withunbranched dicarboxylic acids.

In another advantageous variant, the at least one monoalcohol, however,may also be branched. The use of branched monoalcohols, under somecircumstances, can lower the pour point and increase the flashpoint,which may be advantageous for specific applications. In addition, esteroils with branched monoalcohols, under some circumstances, have higherseal compatibilities.

Branched monoalcohols have been found to be advantageous especially incombination with unbranched polycarboxylic acids and especiallyunbranched dicarboxylic acids. Branched polycarboxylic acids, especiallybranched dicarboxylic acids, are advantageously used in combination withunbranched monoalcohols.

In principle, however, it is also possible to use branched monoalcoholsin combination with branched polycarboxylic acids.

Branched monoalcohols advantageously have a terminal iso branch. Thismean, more particularly, that a methyl group is arranged or branches offat the second position of the remote end of the carbon chain from thealcohol group. Ester oils comprising monoalcohols with terminal isobranches have been found to be advantageous in practice, particularlyfor lubricants and hydraulic oils, and these can at the same time beprepared relatively inexpensively from renewable raw materials.

In principle, differently branched monoalcohols are also usable. Undersome circumstances, however, this results in ester oils which aredifficult and costly to prepare and/or are less suitable for lubricantsor hydraulic oils.

The at least one monoalcohol particularly advantageously has 6-24,preferably 8-16, carbon atoms. Especially preferably, the at least onemonoalcohol has 9, 11, 12, 14 and/or 16 carbon atoms. Such monoalcoholscan firstly be obtained economically from renewable raw materials, andsecondly enable the preparation of a wide range of ester oils which areparticularly suitable as lubricants or hydraulic oils. This is the caseespecially in combination with a polycarboxylic acid or a dicarboxylicacid having 6-13 carbon atoms.

In principle, however, it is also possible to provide monoalcoholshaving fewer than 6 or more than 16 carbon atoms. According to thedesired properties of the ester oils, this may also be advantageousunder some circumstances.

Advantageously, the at least one monoalcohol is a fatty alcohol andespecially an unbranched fatty alcohol from the group of 2-octanol(C₈H₁₈O), 1-nonanol (C₉H₂₀O), 1-undecanol (C₁₁H₂₄O), 1-dodecanol(C₁₂H₂₆O), 1-tetradecanol (C₁₄H₃₀O), and/or cetyl alcohol (also known as1-hexadecanol; C₁₆H₃₄O). Such monoalcohols are especially obtainableeconomically from renewable raw materials and are particularly suitablefor the inventive ester oils. It may likewise be advantageous to usemixtures of two or even more different fatty alcohols. Such mixtures arealso referred to as cuts.

Fatty alcohols are commonly supplied as mixtures or cuts of variouscarbon chain lengths. In the present case, the following cuts areespecially suitable: C8-C10 fatty alcohols and/or C16-C18 fattyalcohols. These can be used to form, for example, the following esterproducts: dialkyl(C8-10)nonanedioate [CAS #: 92969-93-2],dialkyl(C16-18)nonanedioate [CAS #: 92969-94-3],monoalkyl(C8-10)nonanedioate [CAS #: 92969-95-4] and/ormonoalkyl(C16-18) nonanedioate [CAS #: 92969-96-5].

In a further advantageous variant, the at least one monoalcoholcomprises methyltetradecanol (13-methyl-1-tetradecanol; C₁₅H₃₃O). Thisis a saturated, terminally iso-branched monoalcohol.

The monoalcohols mentioned in the last two paragraphs have been found tobe advantageous particularly in combination with polycarboxylic acids,especially dicarboxylic acids having 6-13 carbon atoms, more preferably8-13 carbon atoms. Particularly suitable combinations are those withadipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioicacid and/or brassylic acid.

However, other alcohols and/or combinations with other polycarboxylicacids are also possible in principle.

More preferably, the polycarboxylic acid is a dicarboxylic acid having12 carbon atoms, especially 1,12-dodecanedioic acid, and the at leastone monoalcohol is an alcohol having 13 carbon atoms, more preferably1-tridecanol and/or isotridecanol. Such ester oils have been found to beparticularly advantageous for lubricants and hydraulic oils in terms ofthe preparation and the properties.

A particularly suitable esterification product in the context oflubricants and/or hydraulic oils has been found to be that of thedicarboxylic acid dodecanedioic acid and the monoalcohol isotridecanol.The diisotridecyl dodecanedioate formed [C₃₈H₇₄O₄; M_(w)=595.0] isconvincing especially with regard to viscometric properties (NOACKvalue) and flashpoint, and even as an unadditized base oil hassignificant advantages over known fully formulated lubricants (see alsotables 2 and 3).

According to the application, however, other inventive ester oils mayalso be more advantageous.

A further solution to the problem addressed by the invention is definedby the features of claims 18 and 42.

A second aspect of the invention relates to an ester oil, especially forproduction of a hydraulic oil and/or of a lubricant, comprising anesterification product of at least one monocarboxylic acid with at leastone dialcohol, the dialcohol and/or the monocarboxylic acid originatingfrom renewable raw materials.

In a process for preparing such an ester oil, especially for use in ahydraulic oil and/or a lubricant, a dialcohol is reacted with amonocarboxylic acid to give an ester oil, the dialcohol and/or themonocarboxylic acid originating from renewable raw materials.

In principle, dialcohol and/or the monocarboxylic acid may alsooriginate from mixtures of renewable and fossil raw materials. It isthus not obligatory that the dialcohol and/or the monocarboxylic acidoriginate exclusively from renewable raw materials. In a preferredvariant, however, the dialcohol and/or the monocarboxylic acid originateessentially exclusively from renewable raw materials.

A dialcohol in this context is especially understood to mean an organiccompound having exactly two hydroxyl groups. Dialcohols can also bereferred to as diols and/or dihydric alcohols.

The inventive ester oils according to the second aspect have been foundto be unexpectedly advantageous. In particular, such ester oils aresuitable for lubricants and hydraulic oils. For instance, the ester oilssimultaneously have good lubricant properties and high air separationcapacity. It has likewise been found that the ester oils have a highlifetime or aging resistance compared to known lubricant oils.

In addition, the inventive ester oils have a high flashpoint, and so useis also possible at relatively high temperatures without risk. Moreover,the pour point of the ester oils is relatively low, as a result of whichthe ester oils are also usable at low temperatures. It is thus possibleto use the inventive ester oils within a broad temperature range.

The viscosity of the inventive ester oils is additionally within anideal range for lubricant oils and hydraulic fluids. Adjustment of theviscosity by mixing with another, for example thicker, oil is thus notrequired. It is thus also possible to use the inventive ester oils atelevated temperatures without occurrence of changes in viscosity in theester oil, as is the case for mixed oils owing to the differentvaporization properties of the individual oil components.

Addition of viscosity-modifying thickeners, which is usuallydisadvantageous, is also not required in the case of the inventive esteroils owing to the relatively high viscosity and the high viscosity index(VI), which characterizes the temperature dependence of the kinematicviscosity of a lubricant oil. The air separation capacity of the esteroils is thus not impaired, since emulsified air bubbles in the ester oilcan be separated out more easily. In addition, the problem of softeningof seals, for example in hydraulic systems, barely arises with theinventive ester oils.

Owing to the relatively high viscosity index (VI), the ester oilsexhibit a relatively small temperature-dependent change in viscosity,which is very advantageous in practice for most applications, since theyare usable with relatively constant properties within a broadtemperature range.

As has been found, the vaporization losses (NOACK) of the inventiveester oils are also relatively low.

In addition, the use of renewable raw materials enables particularlyenvironmentally friendly and economic production. More particularly,through the use of renewable raw materials, the inventive ester oils aresimultaneously also convincing in terms of toxicology andbiodegradability. Essentially all of the inventive ester oils haverelatively rapid and easy biodegradability.

Compared to the ester oils according to the first aspect, monocarboxylicacids are used directly for the preparation of the ester oils in thesecond aspect of the invention. Monocarboxylic acids are available onthe market with a wide variety of different structures, which allows theproperties of the ester oils to be adjusted in a relatively simple andcontrolled manner through the use of specific monocarboxylic acids. Inaddition, the monocarboxylic acids used may also be fatty acidsobtainable directly from renewable raw materials or vegetable oils. Thishas been found to be particularly economically viable.

The dialcohol preferably originates from renewable raw materials. Thishas been found to be advantageous particularly with regard to theeconomic viability of the preparation. Dialcohols can be produced, forexample, by oleochemical means in a manner known per se. For example, amultitude of different polycarboxylic acids are obtainable by oxidativecleavage from vegetable oils, and these can then be converted byreduction to dialcohols. Corresponding vegetable oils are alreadyavailable globally in large volumes. It is thus possible to obtain amultitude of different polycarboxylic acids from renewable raw materialsor vegetable oils in relatively simple chemical process steps, and thesecan be converted to corresponding dialcohols. In addition, compliancewith current environmental regulations or ecolabels is enabled.

However, it is also possible in principle to use, for example,dialcohols produced by petrochemical means from fossil raw materials, ifthis appears appropriate to the purpose.

The dialcohol is preferably saturated. In other words, there arepreferably only single bonds between the carbon atoms of the dialcohol.It is thus possible to improve particularly the oxidation resistance andstability of the ester oil.

In principle, the dialcohol may also be mono- or polyunsaturated.

In a further preferred variant, the dialcohol is unbranched. In otherwords, the dialcohol preferably has an unbranched carbon chain, which isespecially linear. This has been found to be especially advantageous fora multitude of applications of the ester oil.

In another, likewise advantageous variant, the dialcohol is branched,especially singly or multiply methyl-branched. This means, moreparticularly, that the dialcohol has a carbon chain from which at leastone methyl group (—CH₃) branches off. More particularly, the dialcoholmay, for example, be a trimethylhexanediol (TMH). Together withisononanoic acid, the result is, for example, an esterification productwith low thermal viscosities and pour points (η_(100° C.)=4.56 mm²/s,η_(−40° C.)=14.165 mm²/s (capillary), VI=123, pour point=−51° C.)

Whether an unbranched or branched dialcohol is more advantageous dependsupon factors including the monocarboxylic acids used for the ester oiland the desired substance properties of the ester oil. The use ofbranched dialcohols, under some circumstances, can lower the pour pointand increase the flashpoint, which may be advantageous for specificapplications. In addition, ester oils with branched dialcohols, undersome circumstances, have higher seal compatibilities. Especially methylbranches have been found to be particularly advantageous.

In principle, however, in place of or in addition to methyl branches,other branches are also possible, for example ethyl and/or propylbranches.

Advantageously, the dialcohol has 5-14 carbon atoms. Such dialcohols canfirstly be obtained economically from renewable raw materials, andsecondly enable the production of a wide range of ester oils which areparticularly suitable as lubricants or hydraulic oils.

However, it is also possible in principle to provide dialcohols havingfewer than 5 or more than 14 carbon atoms. According to the desiredproperties of the ester oils, this may also be advantageous.

More preferably, the dialcohol is a terminal dialcohol. In terminaldialcohols, the alcohol groups are arranged at the ends of the carbonchain of the alcohol. It is thus possible to form, together withmonocarboxylic acids, ester oils which are particularly suitable aslubricants and hydraulic oils. In addition, the production of terminaldialcohols from renewable raw materials, for example vegetable oils, ispossible without any problem, which is to the benefit of economicviability.

The dialcohol advantageously comprises one or more representatives fromthe group of 1,6-hexanediol (HO—C₆H₁₂—OH), 1,7-heptanediol(HO—C₇H₁₄—OH), 1,8-octanediol (HO—C₈H₁₆—OH) 1,9-nonanediol (HO—C₉H₁₈—OH)1,10-decanediol (HO—C₁₀H₂₀—OH), 1,12-dodecanediol (HO—C₁₂H₂₄—OH),1,13-tridecanediol (HO—C₁₃H₂₆—OH) and/or isomers thereof. Isomers meanespecially compounds which have the same empirical formula but differwith regard to linkage and/or spatial arrangement of the individualatoms. With such dialcohols having 6, 7, 8, 9, 10, 12 or 13 carbonatoms, it is possible to form a multitude of ester oils which can beprepared economically from renewable raw materials and which areparticularly suitable for lubricants and hydraulic oils.

In principle, however, it is also conceivable to use alcohols havingthree or even more hydroxyl groups. It is also possible to use otherrepresentatives of dialcohols than those above, these having, forexample, fewer than 5 carbon atoms or more than 14 carbon atoms.

It may also be advantageous to provide a mixture of at least twodifferent dialcohols. In this case, it is firstly possible to controlthe properties of the ester oils even more precisely, and secondly tofurther optimize the preparation process in terms of economic viability.Advantageously, the at least two different dialcohols originate fromrenewable raw materials.

In a further preferred variant, the at least one monocarboxylic acidoriginates from renewable raw materials. It is thus possible to preparethe inventive ester oils, for example, in a particularly economicallyviable manner in few process steps via fatty acids from vegetable oils.The fatty acids can be used directly without any need to convert them toalcohols or other derivatives in additional reaction steps. Since atleast two moles of monocarboxylic acid can be converted per mole ofdialcohol in each case, it is additionally possible through the use ofmonocarboxylic acids from renewable raw materials to achieve arelatively high proportion of renewable raw materials in the reactionproduct or the ester oil. This also simplifies compliance with currentenvironmental regulations or ecolabels.

More preferably, both the dialcohol and the monocarboxylic acidoriginate from renewable raw materials. It is thus possible to furtherimprove the aforementioned advantages.

However, it is also possible in principle to use monocarboxylic acidsfrom fossil raw materials, if this appears appropriate to the purpose.

The at least one monocarboxylic acid is preferably saturated. In otherwords, there are preferably only single bonds between the carbon atomsof the at least one monocarboxylic acid. It is thus possible to improveespecially the oxidation resistance and stability of the ester oil.

In a particularly advantageous variant, both the dialcohol and the atleast one monocarboxylic acid are saturated. This greatly improves theoxidation resistance and aging resistance.

Advantageously, the at least one monocarboxylic acid is unbranched.Thus, the at least one monocarboxylic acid advantageously has anunbranched carbon chain, which is especially linear. This has been foundto be advantageous for a multitude of applications, especially withregard to an optimal viscosity of the ester oil. This is the caseespecially for a combination with unbranched dialcohols.

In another advantageous variant, the at least one monocarboxylic acid,however, may also be branched.

Especially suitable are monocarboxylic acids which are singly ormultiply methyl-branched. The monocarboxylic acid more preferably has aterminal iso branch. The use of such branched monocarboxylic acids can,under some circumstances, lower the pour point and increase theflashpoint, which may be advantageous for specific applications. Inaddition, ester oils with branched monocarboxylic acids, under somecircumstances, have higher seal compatibilities.

Branched monocarboxylic acids have been found to be advantageousespecially in combination with unbranched dialcohols and especiallyunbranched dialcohols. Branched dialcohols, especially brancheddialcohols are advantageously used in combination with unbranchedmonocarboxylic acids.

In principle, however, it is also possible to use branchedmonocarboxylic acids in combination with branched dialcohols.

More particularly, the at least one monocarboxylic acid has 6-18 carbonatoms, preferably 9-16 carbon atoms. Such monocarboxylic acids canfirstly be obtained economically from renewable raw materials, forexample in the form of fatty acids from vegetable oils, and secondlyenable the production of a wide range of ester oils which areparticularly suitable as lubricants or hydraulic oils. This is the caseespecially in combination with dialcohols having 5-14 carbon atoms.

In principle, however, it is also possible to provide monocarboxylicacids having fewer than 6 or more than 18 carbon atoms. According to thedesired properties of the ester oils, this may also be advantageousunder some circumstances.

Advantageously, the at least one monocarboxylic acid is a fatty acid,and the at least one monocarboxylic acid especially comprises one ormore representatives from the group of caprylic acid (C₇H₁₅—COOH; alsoreferred to as octanoic acid), pelargonic acid (C₈H₁₇—COOH; alsoreferred to as nonanoic acid), capric acid (C₉H₁₉—COOH; also referred toas decanoic acid), undecanoic acid (C₁₀H₂₁—COOH), lauric acid(C₁₁H₂₃—COOH; also referred to as dodecanoic acid), tridecanoic acid(C₁₂H₂₅—COOH), myristic acid (C₁₃H₂₇—COOH; also referred to astetradecanoic acid), hexanedecanoic acid (C₁₅H₃₁—COOH, also referred toas palmitic acid), octanedecanoic acid (C₁₇H₃₅—COOH, also referred to asstearic acid) and/or isomers thereof. Such monocarboxylic acids areespecially obtainable economically from renewable raw materials and areparticularly suitable for the inventive ester oils.

The monocarboxylic acids mentioned in the last paragraph have been foundto be advantageous particularly in combination with polyalcohols,especially dialcohols, having 5-14 carbon atoms. Particularly suitablecombinations are those with one or more representatives from the groupof 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol,1,10-decanediol, 1,12-dodecanediol, 1,13-tridecanediol and/or isomersthereof.

However, it is also possible in principle to use other dialcohols and/orcombinations with other polycarboxylic acids.

In a further optional variant, the monocarboxylic acid is a cyclicmonocarboxylic acid, especially a saturated cyclic monocarboxylic acid.A suitable example is CH₃—(CH₂)_(x)—C₆H₁₀—(CH₂)_(y)—COOH, where x+y=10,more preferably 9-(2′-n-propylcyclohexyl)nonanoic acid[CH₃—(CH₂)₂—C₆H₁₀—(CH₂)₈—COOH]. This can be obtained directly fromlinseed oil, which is present in the seeds of flax, by alkalineisomerization [on this subject, see Beal et al.; JAOCS 42, 1115-1119(1965)].

More preferably, the dialcohol is a dialcohol having 12 carbon atoms,especially 1,12-dodecanediol, and the at least one monocarboxylic acidis a monocarboxylic acid having 13 carbon atoms, more preferably1-tridecanoic acid and/or isotridecanoic acid. Such ester oils have beenfound to be particularly advantageous for lubricants and hydraulic oilsin terms of the preparation and the properties.

In both aspects of the invention, the inventive ester oil, based on thecarbon content, is formed from renewable raw materials preferably to anextent of at least 25 mol %, further preferably at least 50 mol %, evenfurther preferably at least 60 mol %, especially preferably at least 70mol %. In a very particularly preferred embodiment, the inventive esteroil is formed exclusively from renewable raw materials apart fromunavoidable impurities.

It is thus possible to produce high-performance ester oils particularlysuitable for lubricants and hydraulic fluids in an economic manner,these additionally also being able to satisfy current and futureenvironmental regulations.

In principle, a lower proportion than 25% of renewable raw materials mayalso be present. However, the aforementioned advantages are absent undersome circumstances.

As has been found, a molecular weight of the esterification product isadvantageously at least 400 g/mol, especially at least 550 g/mol. Thisis true of both aspects of the invention. It has been found that suchester oils are of particularly good suitability especially as lubricantsand hydraulic oils. The reason for this might be that the substanceproperties of particular relevance for lubricants and hydraulic oils(viscosity, viscosity index, flashpoint or pour point) in the case ofsuch ester oils are all within a practicable to ideal range.

However, ester oils having a lower molecular weight than 500 g/mol arealso possible. This, however, may be disadvantageous for particularapplications of the ester oils.

The esterification product preferably has at least 30 carbon atomsand/or at most 50 carbon atoms. As has been found, esterificationproducts having at least 30 carbon atoms result in sufficiently highviscosity values, such that the corresponding ester oils are especiallysuitable for hydraulic oil and/or lubricant. The necessity of additionof additives to improve the viscosity level can be significantly reducedas a result, or becomes entirely unnecessary. In addition, it has beenfound that ester oils comprising esterification products having at most50 carbon atoms are particularly suitable with regard to flow propertiesfor hydraulic oils and/or lubricants. Particularly advantageously, theester oils comprise esterification products having at least 30 carbonatoms and/or at most 50 carbon atoms. It is thus unexpectedly possibleto simultaneously lower the pour points and increase the viscositylevel.

In principle, the ester oils may also comprise esterification productswhich have fewer than 30 carbon atoms and/or more than 50 carbon atoms.This may even be appropriate for specific applications.

The inventive ester oils can particularly be used as lubricant and/orhydraulic oil. This is true both of ester oils according to the firstaspect and of ester oils according to the second aspect.

Lubricants and/or hydraulic oils comprising an inventive ester oilpreferably have a proportion of ester oil of at least 50% by weight,preferably at least 75% by weight, further preferably at least 90% byweight, even more preferably at least 93% by weight, still furtherpreferably at least 96% by weight, measured by the total weight of thelubricant.

Smaller proportions of ester oil are also possible, but the lubricant orhydraulic fluid then under some circumstances no longer have theaforementioned advantageous properties.

In a preferred variant, the lubricant and/or the hydraulic fluidcomprises additives for improving the properties.

Advantageously, the additives used are antioxidants, antiwear additives,metal deactivators, corrosion inhibitors and/or antifoams.

Advantageous antioxidants are especially aminic anti-oxidants and/orphenolic antioxidants. Suitable aminic antioxidants are alkylateddiphenylamines (alkylated DPA) and/or N-phenyl-alpha-naphthylamine(PANA). A proportion of the aminic antioxidants is especially 0.01-3% byweight, more preferably 0.1-0.5% by weight.

Advantageous phenolic antioxidants are especially butylhydroxytoluene(BHT), 2,6-di-tert-butylphenol (2,6-DTBP) and/or derivatives of3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. Particularly suitablederivatives are octadecyl3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and pentaerythrityltetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. Likewiseadvantageous are, for example,6,6′-di-tert-butyl-2,2′-methylenedi-p-cresol [CAS #: 119-47-1] and4,4′-methylenebis-2,6-di-tert-butylphenol [CAS #: 118-82-1]. Aproportion of the phenolic antioxidants is especially 0.01-5% by weight,more preferably 0.3-0.7% by weight.

More particularly, the lubricant and/or the hydraulic fluid compriseboth aminic antioxidants and phenolic antioxidants.

Advantageously, ashless antiwear additives are used. Antiwear additivessuch as zinc dithiophosphates, for example, are therefore preferably notused. Suitable antiwear additives are especially amine phosphates,alkylated phosphates, for example tricresyl phosphate, triphenylphosphorothionate and/or thionated esters. A proportion of the antiwearadditives is advantageously 0.01-3% by weight, especially 0.6-1.0% byweight.

Advantageous metal deactivators have been found to be especiallybenzotriazole, tolutriazole and corresponding Mannich bases and/orderivatives of 2,5-dimercapto-1,3,4-thiadiazole. A proportion of themetal deactivators is advantageously 0.01-1% by weight, preferably0.02-0.1% by weight.

Suitable corrosion inhibitors are, for example, alkylated succinic acidand/or derivatives thereof, for example monoesters, monoamides and/oramine phosphates.

The proportion of corrosion inhibitors is especially 0.01-3% by weight,preferably 0.1-0.4% by weight.

Suitable antifoams are especially alkyl polyacrylates, methacrylatederivatives and/or polydimethylsiloxane (PDMS). An advantageousproportion is 0.001-0.1% by weight, preferably 0.01-0.03% by weight.

The aforementioned antioxidants, antiwear additives, metal deactivators,corrosion inhibitors and/or anti-foams are, in particular, chemicallycompatible with the inventive ester oils. With the proportionsspecified, optimal effects are additionally achieved, without impairingthe performance of the lubricants and/or hydraulic fluids. In principle,however, it is also possible to use additional and/or other additives.It is also possible to dispense with individual additives or all of theadditives mentioned.

The monocarboxylic acids, polycarboxylic acids, monoalcohols and/ordialcohols used for preparation for the ester oils are preferablyprepared from fatty acids from renewable raw materials. Especiallysuitable are palm oil and/or fatty acids such as oleic acid (C18:1; 9Z;ω-9), linoleic acid (C18:2; 9Z, 12Z; ω-6), gadoleic acid (C20:1; 11Z,ω-9), erucic acid (C22:1, 13Z; ω-9), petroselinic acid (C18:1; 6Z; ω-6),arachidonic acid (C20:4; 5Z, 8Z, 11Z, 14Z; ω-6) and/or generallyω-6-fatty acids. The number which follows the letter “C” after the nameof the fatty acid in each case indicates the number of carbon atoms.Separated by a colon, there follows the number of double bonds in thefatty acid and details of position and configuration (Z, E) of thedouble bonds in the carbon chain. Likewise listed is the ω type of thefatty acid or the position of the first double bond based on the lastcarbon atom furthest removed from the carboxyl group (“ω”) in the carbonchain.

Especially suitable for preparation of the monocarboxylic acids,polycarboxylic acids, monoalcohols and/or dialcohols used for the esteroils are also hydroxy fatty acids, especially ricinoleic acid (C18:1;9Z; 12R; 12-hydroxy; ω-9), lesquerolic acid (C20:1; Z11; 14-hydroxy)and/or vernolic acid (C18:1; 9Z; 13-epoxy; ω-9).

Such raw material sources allow, more particularly, economically viableproduction of ester oils for lubricants and hydraulic oils. The personskilled in the art is aware of a multitude of vegetable oils and/oranimal fats from which the aforementioned fatty acids can be obtained.

In principle, however, it is also possible to resort to other sources ifthis appears more advantageous.

The detailed description which follows and the entirety of the claimsgive rise to further advantageous embodiments and feature combinationsof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended drawing show:

FIG. 1 a diagram which shows the coefficients of friction (f) as afunction of time or standard force in a friction-wear test (to SRV III;and standard ASTM D 7421-08) for three selected ester oils compared toDITA and TMP;

FIG. 2 a,b four diagrams which show the coefficients of friction (f),the standard force (F_(N)) and stroke (dx) in the friction-wear test onwhich FIG. 1 is based with diisotridecyl adipate as a function of time;

FIG. 3 a,b four diagrams which show the coefficients of friction (f),the standard force (F_(N)) and stroke (dx) in the friction-wear test onwhich FIG. 1 is based with di(isotridecyl) dodecanedioate (C12D13) as afunction of time;

FIG. 4 a,b four diagrams which show the coefficients of friction (f),the standard force (F_(N)) and stroke (dx) in the friction-wear test onwhich FIG. 1 is based with trimethylolpropane ester (TMP-C8/C10) as afunction of time.

WAYS OF PERFORMING THE INVENTION A) Carboxylic Acids Fatty Acids

Fatty acids, such as oleic acid, linoleic acid, gadoleic acid, erucicacid, petroselinic acid, arachidonic acid, or ω-6-fatty acids ingeneral, can be obtained, for example, in a manner known per se by meansof alkaline hydrolysis from the corresponding triacyl glycerides. Thisinvolves boiling the corresponding fats or oils with bases. The saltsobtained can then be neutralized with acids, which gives free fattyacids or mixtures of free fatty acids. Separation of the different fattyacids in the mixtures is effected, for example, by a distillativeseparation process.

Oleic acid can be obtained, for example, from olive oil, peanut oil,avocado oil, goose fat, palm oil, pork fat, sesame oil, mutton tallow,beef tallow and sunflower oil. Linoleic acid is obtainable, for example,from safflower oil, sunflower oil, soya oil, corn kernel oil and oliveoil. Gadoleic acid is present in jojoba oil, while erucic acid occurs invarious rapeseed oil varieties and sea kale species. In addition,petroselinic acid can be obtained from coriander oil, and arachidonicacid from animal fats or fish oil.

Hydroxy Fatty Acids

Ricinoleic acid can be obtained, for example, by hydrolysis of castoroil, in which the substance occurs in the form of triglycerides.Lesquerolic acid is obtainable especially from the oil from Lesquerellaof fendleri seeds, while vernolic acid is obtainable from the seeds ofVernonia galamensis, a plant from the sunflower family, by extraction.

Adipic Acid (C6)

Adipic acid [Chemical Abstracts number (CAS #): 124-04-09;HOOC—(CH₂)₄—COOH; molecular weight (M_(w))=146.14] can be obtained bypetrochemical means from cyclohexane by double oxidation, for examplewith nitric acid, or from cyclohexanol [K. Saro et al., “A green routeto adipic acid: direct oxidation of cyclohexene with 30 percent hydrogenperoxide”, Science, Vol. 281, p. 1646-1647 (1998)]. Another possibilityis oxidation of cyclohexene by means of H₂O₂ (30%) using a phasetransfer catalyst (quaternary ammonium hydrosulfate orNa₂WO₂+[CH₃(n-C₈H₁₇)₃N]HSO₄).

Adipic acid from renewable raw materials can be obtained, for example,from xylose derivatives (C₅ sugars), by decarbonylation of furfurylalcohol (furfural, C₅H₄O₂). It can likewise be obtained from glucose (C₆sugar), in the form of sorbitol, or from D-glucose [K. M. Drahts et al.,J. Am. Chem. Soc. 1994, Vol. 116, p. 399-400] via cis,cis-muconic acid[CAS #: 1119-72-81] and 5-hydroxymethylfurfural (5-HMF) by thermaldecomposition from sugar. In addition, it is possible to obtain adipicacid via an oxidative cleavage of an ω-6-fatty acid, for examplegamma-linolenic acid [C₁₈H₃₀O₂; M_(w)=278.43].

The oxidative cleavage of gamma-linolenic acid as ω-6-fatty acid gives 2mol of adipic acid as well as 2 mol of malonic acid, which constitutesan effective yield.

It is also possible to prepare adipic acid by oxidative cleavage ofarachidonic acid [CAS #: 506-32-11; C₂₀H₃₂O₂; M_(w)=304.46].

The latter can in turn be prepared via mono- and diasaccharides,hemicellulose (wood cooking), petroselinic acid and/or 1,4-butanediol.Likewise possible is enzymatic synthesis from ammonium adipate withgenetically modified microorganisms. In this regard, reference is madeto U.S. Pat. No. 5,629,190.

Petroselinic acid [CAS #: 593-39-51, C₁₈H₃₄O₂; M_(w)=282.46], an isomerof oleic acid, as the cis or trans stereoisomer, has an unsaturated bondat C6, which can be oxidatively cleaved in order to directly obtainadipic acid, additionally giving lauric acid, i.e. n-dodecanoic acid (aC12-monocarboxylic acid; M_(w)=200.31). The latter can then be reduced,for example with lithium aluminum hydride, to 1-dodecanol (laurylalcohol; C₁₂H₂₆O; M_(w)=186.33). Petroselinic acid itself is present incoriander seeds, but also in fennel.

Branched Adipic Acid Derivatives (C9)

3-Methyladipic acid [CAS #: 3058-01-3; C₇H₁₂O₄; M_(w)=160.2], a singlymethyl-branched adipic acid, can be obtained from cresol viamethylcyclohexanone and is also commercially available (for example fromSigma-Aldrich).

2,2,3-Trimethyladipic acid [CAS #: 28472-18-6; C₉H₁₆O₄; M_(w)=188.2],2,2,4-trimethyladipic acid [CAS #: 3586-39-8; C₉H₁₆O₄; M_(w)=188.2] and2,4,4-trimethyladipic acid [CAS #: 3937-59-5; C₉H₁₆O₄; M_(w)=188.2] aremultiply methyl-branched derivatives of adipic acid which are likewisecommercially available.

Azelaic Acid (C9)

Azelaic acid [CAS #: 123-99-9; C₉H₁₆O₄; with M_(w)=188.22] is obtainableby an oxidative cleavage at the respective double bond of oleic acid,i.e. cis-9-octadecenoic acid [CAS #: 112-80-1; C18:1; cis-9] by means ofozone (ozonolysis) at approx. 100° C. or the reagents H₂O₂, NaOCl (withruthenium catalyst), hot nitric acid, KMnO₄ or chromic acid. Aby-product additionally obtained is pelargonic acid [CAS #: 112-05-0;C₉H₁₈O₂; with M_(w)=158.24; also called nonanoic acid], a monocarboxylicacid. In this regard, reference is also made to U.S. Pat. No. 2,823,113and U.S. Pat. No. 5,336,7931.

The same applies mutatis mutandis in the case of use of elaidic acid,i.e. trans-9-octadecenoic acid [CAS #: 112-79-8; C₁₈H₃₄O₂], whichcorresponds to the trans isomer of oleic acid.

The pelargonic acid obtained can be reduced to 1-nonanol [CAS #:143-08-61, M_(w)=144.29] as a C₉ alcohol, in order to use it as arenewable alcohol in a dicarboxylic ester.

Azelaic acid, however, is also obtainable in the same way from gadoleicacid, i.e. eicosenoic acid [CAS #: 267634-41-0; C20:1; (−9;M_(w)=310.51] by oxidative cleavage. A by-product formed is undecanoicacid [CAS #: 112-37-8; M_(w)=186.30] as a C_(1l)-monocarboxylic acid,which can be reduced to n-undecanol [CAS #: 112-45-2; C₁₁H₂₄O;M_(w)=172.30].

Brassylic Acid (C13)

Brassylic acid is obtainable via cis-erucic acid, i.e. cis-13-docosenoicacid [CAS #: 112-86-7; C22:1; co-13; M_(w)=338.56] or the trans isomer,trans-13-docosenoic acid, present in rapeseed oil, mustard oil orAbyssinian sea kale. By oxidative cleavage (in the same way as describedfor azelaic acid), pelargonic acid is formed as the monocarboxylic acid,and brassylic acid, i.e. tridecanedioic acid [CAS #: 505-52-2; C₁₃H₂₄O₄;M_(w)=244.3], as the saturated C₁₃ dicarboxylic acid.

Suberic Acid (C8)

Suberic acid can be obtained by petrochemical means, by ozonolysis ofcyclooctene. On the basis of renewable raw materials, it can be obtainedessentially from cork and potato peelings.

Cork powder can be cleaved to suberic acid by oxidation with HNO₃.Likewise possible is the oxidative cleavage of ricinoleic acid, palm oiland oleic acid, in which not only azelaic acid but also suberic acid isformed [see, for example, R. G. Kadesch; J. Am. Oil Chemists' Soc. Vol.56, p. 845A-849A (1979) and references mentioned therein].

Specifically, suberic acid, i.e. octanedioic acid [CAS #: 505-48-6;C₈H₁₄O₄; M_(w)=174.19], for example in the case of a suitable reactionregime, is obtainable by an oxidative cleavage at the double bond ofricinoleic acid [CAS #: 141-22-0, 8040-35-5; 17026-54-9; 25607-48-1;45260-83-1; C₁₈H₃₄O₃; M_(w)=298.46], a 12-hydroxy-9-octadecenoic acid(C18:1) from castor oil [J. W. Hill et al., Organic Syntheses, Coll.Vol. 2, p. (1943) and Vol. 56, p. 4 (1933); M. J. Diamond et al., J. Am.Oil Chemists' Soc., Vol. 42, p. 882-884 (1965); R. G. Kadesch; J. Am.Oil Chemists' Soc. Vol. 31, p. 568-573 (1954)].

By an alkaline cleavage with NaOH at 180-270° C., sebacic acid sodiumsalt and 2-octanol, i.e. capryl alcohol [C₈H₁₈O; M_(w)=130.22], areobtained.

Dodecanedioic Acid (C12)

The seed of Lesquerella contains approx. 55-60% of the hydroxy fattyacid 14-hydroxy-cis-11-eicosanoic acid [CAS #: 4103-20-2; C₂₀H₃₈O₃;M_(w)=326.51], which can likewise be cleaved oxidatively in NaOH at180-250° C. to dodecanedioic acid [C₁₂H₂₂O₄] and 2-octanol, and also12-hydroxydodecanoic acid [CAS #: 505-95-31] and 2-octanone [CAS #:111-13-7].

B) Preparation of Monoalcohols 2-Octanol, 1-nonanol, n-undecanol and1-dodecanol

Possible sources and processes for preparing 2-octanol [C₈H₁₈O;M_(w)=130.22], 1-nonanol [CAS #: 143-08-61, C₉H₂₀O; M_(w)=144.29],n-undecanol [CAS #: 112-45-2; C₁₁H₂₄O; M_(w)=172.30], 1-dodecanol(lauryl alcohol; C₁₂H₂₆O; M_(w)=186.33) have already been mentionedabove in the context of the preparation of dicarboxylic acids fromrenewable raw materials.

Isononanol

3,5,5-Trimethylhexyl alcohol, i.e. isononyl alcohol [CAS #: 3452-97-9;C₉H₂₀O; M_(w)=144.3], a highly branched isomer of nonanol, is sold byExxon and Kyowa Hakko Kogyo Co. Ltd.

1-Decanol

1-Decanol [CAS #: 112-30-1; C₁₀H₂₂O; M_(w)=158.3] is obtainable, forexample, by hydrogenation of capric acid (C₉H₁₉COOH). Capric acid itselfoccurs, for example, bound in triglycerides in vegetable oils, and isalso present in palm oil, coconut oil, and in goats' milk fat.

Isodecanol

Isodecanol [CAS #: 25399-17-7; C₁₀H₂₂O; M_(w)=158.3] is obtainable, forexample, under the “EXXAL” trade name via Exxon. In addition, mixtureswith C₉-C₁₁ alcohols rich in C₁₀ alcohols are also supplied commercially[CAS #: 93821-11-5 or 68526-85-2].

1-Tridecanol

1-Tridecanol, i.e. n-tridecanol [CAS #: 112-70-9; C₁₃H₂₈O; M_(w)=200.4],is commercially available with a purity of >98% (for example fromSigma-Aldrich). However, various mixtures comprising 1-tridecanol arecommercially available, for example a mixture of 1-tridecanol with1-dodecanol [CAS #: 90583-91-8] from BASF, or a mixture of C₁₀-C₁₇alcohols also comprising the C₁₋₃ alcohols under the “Neodol 25” namefrom Shell. Another possible preparation is the reduction of tridecanoicacid [CAS #: 638-53-9; C₁₃H₂₆O₂; M_(w)=214.3], which is found in somevegetable oils, for example in the seeds of the Australian plantStackhousia tryonii).

Isotridecanol

Isotridecanol, i.e. 11-methyldodecanol [CAS #: 27458-92-0; C₁₃H₂₈O;M_(w)=200.4] is obtainable on the basis of propylene tetramer [CAS #:6842-15-5] or tetrapropylene/1-dodecene [CAS #: 112-41-4] and via basicoxidation at 250-300° C. Isotridecanol is sold commercially, for exampleby Exxon under the EXXAL13 product name.

1-Tetradecanol

1-Tetradecanol or myristyl alcohol [CAS #: 112-72-1; C₁₄H₃₀O;M_(w)=214.4], also defined in a technical commercial context as amixture of straight-chain and 100% linear C₁₂-C₁₆ alcohols with acontent of >95% of C₁₄ alcohols, can be obtained by reduction ofmyristic acid C14:0 [CAS #: 544-63-81], which is present in coconut oilto an extent of approx. 15-21% and in palm kernel oil to an extent ofapprox. 14-18%.

General Fatty Alcohols

It is common knowledge that fatty alcohols can be obtained directly fromvegetable raw materials. Fatty alcohols having 8 carbon atoms (C8) to 18carbon atoms (C18), for example 1-octanol [CAS #: 111-87-5; C₈H₁₈O],decanol, dodecanol (lauryl alcohol); tetradecanol (myristyl alcohol),hexadecanol [CAS #: 36653-82-4; C₁₈H₃₄O; M_(w)=242.44; also called cetylalcohol] and/or octadecanol [CAS #: 112-92-5; C₁₈H₃₈O; M_(w)=270.5; alsocalled stearyl alcohol], can be prepared, for example, by reduction ofcorresponding esters with sodium (Bouveault-Blanc reaction). It is alsopossible to prepare fatty alcohols by hydrogenation over copper orcopper/cadmium catalysts. Frequently, fatty alcohols are nowadaysproduced by petrochemical means from mineral oil and are commerciallyavailable as such. Fatty alcohols can be prepared from renewable rawmaterials especially by hydrogenation of fatty acids from vegetableoils. The fatty acids, for example, are reduced with lithium aluminumhydride in a manner known per se to the corresponding fatty alcohols.

C) Preparation of Polyols Neopentyl Glycol

Neopentyl glycol, i.e. 2,2-dimethyl-1,3-propanediol [CAS #: 126-30-7;C₅H₁₂O₂; M_(w)=104.2], is commercially available or can be prepared viahydrogenation of the aldol addition product of isobutyraldehyde andformaldehyde (in this regard, see WO 2008/000650 A1).

1,6-Hexanediol

1,6-Hexanediol [CAS #: 629-11-8; C₆H₁₄O₂; M_(w)=118.2] can be obtained,for example, by reduction of adipic acid with lithium aluminum hydride,or esters thereof with elemental sodium. It is thus possible to prepare1,6-hexanediol from renewable raw materials.

It is also possible to prepare 1,6-hexanediol from glucitol [CAS #:50-70-4; C₆H₁₄O₆; M_(w)=182.2; also called sorbitol]. This involvesreducing glucitol at positions 2, 3, 4 and 5 with elimination of thehydroxyl groups. Glucitol itself is obtainable in a manner known per seby hydrogenation of glucose from cereals, beets or cane sugar.

2,2,4-Trimethyl-1,3-pentanediol

2,2,4-Trimethyl-1,3-pentanediol [CAS #: 144-19-4; C₈H₁₈O₂; M_(w)=146.2]is commercially available (Alfa Aesar, Hangzhou Dayang Chemical Co.,Ltd.).

2-Butyl-2-ethyl-1,3-propanediol

2-Butyl-2-ethyl-1,3-propanediol [CAS #: 115-84-4; C₉H₂₀O₂; M_(w) 160.3]is likewise commercially available (Sigma-Aldrich; Jinan Haohua IndustryCo., Ltd.).

Further Dialcohols

It is possible to form further dialcohols from the aforementioneddicarboxylic acids by reduction, for example with lithium aluminumhydride, these dialcohols being usable for inventive ester oils.

D) Refining

The mono- and dicarboxylic acids and alcohols obtained, for example,from the oxidative cleavage are separated from one another by processesknown per se to those skilled in the art with exploitation of differentsubstance properties, for example melting point, solubilities(extraction, hot water), boiling temperatures (selective distillation)and/or acid cleavage (H₂SO₄), in order to obtain sufficiently puresubstances.

E) Preparation of Diesters on the Basis of Dicarboxylic Esters

Dicarboxylic esters can be prepared in a manner known per se by reactionof dicarboxylic acids with monoalcohols with elimination of water. Theesterification can especially be acid-catalyzed (Fischer esterification)and is well known to those skilled in the art. For the preparation ofdicarboxylic esters, more particularly, 2 mol of monoalcohols arereacted with 1 mol of dicarboxylic acid.

The diesters listed in the table which follows have been found to beparticularly advantageous in the practical test for hydraulic oils. Alldiesters can be produced to an extent of 100% from renewable rawmaterials. In the last column, the maximum proportion of renewable rawmaterials formed from the dicarboxylic acid (Ac) and from themonoalcohols (Al) in the diester is reported in each case.

Dicarboxylic acid Proportion Monoalcohol Dicarboxylic acid of RRM Adipicacid Isodecanol

Ac: 26.3% Al: 73.7% Adipic acid 1-Tridecanol

Ac: 18.8% Al: 81.2% Adipic acid Isotridecanol

Ac: 18.8% Al: 81.2% Adipic acid 1-Tetradecanol

Ac: 18% Al: 82% Azelaic acid 1-Tridecanol

Ac: 26% Al: 74% Dodecanedioic acid 1-Nonanol

Ac: 40.0% Al: 60.0% Dodecanedioic acid Isodecanol

Ac: 37.5% Al: 62.5% Dodecanedioic acid Isotridecanol

Ac: 31.6% Al: 68.4% Dodecanedioic acid 1-Tridecanol

Ac: 31.6% Al: 68.4%

G) Preparation of Ester Oils on the Basis of Diol Esters

Dialcohol esters or diol esters can be obtained by reaction ofdialcohols with monocarboxylic acids. For the preparation of diolesters, more particularly, 2 mol of monocarboxylic acids are reactedwith 1 mol of diol.

The diesters listed in the table below have been found to beparticularly advantageous in the practical test for hydraulic oils. Thediol esters can also be produced to an extent of 100% from renewable rawmaterials. In the last column, the maximum proportion of renewable rawmaterials formed from the diol (Al) and from the monocarboxylic acids(Ac) in the diol ester is reported in each case.

Diol/Mono- carboxylic Proportion acid Diol ester of RRM 1,6-HexanediolIsodecanoic acid

Ac: 23.1% Al: 76.9% 1,6-Hexanediol 1-Tridecanoic acid

Ac: 18.8% Al: 81.2% 1,6-Hexanediol Isotridecanoic acid

Ac: 18.8% Al: 81.2% 1,6-Hexanediol Tetradecanoic acid

Ac: 18% Al: 82% 1,9-Nonanediol 1-Tridecanoic acid

Ac: 26% Al: 74% 1,12-Dodecane- diol Pelargonic acid (nonanoic acid)

Ac: 40.0% Al: 60.0% 1,12-Dodecane- diol Isodecanoic acid

Ac: 37.5% Al: 62.5% 1,12-Dodecane- diol Isotridecanoic acid

Ac: 31.6% Al: 68.4% 1,12-Dodecane- diol 1-Tridecanoic acid

Ac: 31.6% Al: 68.4%

The above-described diesters are merely examples which can be modifiedin the context of the invention.

In the case of the aforementioned diesters based on adipic acid, it isalso possible to replace the adipic acid with one of the followingbranched derivatives: 3-methyladipic acid [CAS #: 3058-01-3, C₇H₁₂O₄;M_(w)=160.2], 2,2,3-trimethyladipic acid [CAS #: 28472-18-6; C₉H₁₆O₄;M_(w)=188.2], 2,2,4-trimethyladipic acid [CAS #: 3586-39-8; C₉H₁₆O₄;M_(w)=188.2] and/or 2,4,4-trimethyladipic acid [CAS #: 3937-59-5;C₉H₁₆O₄; M_(w)=188.2]. It is thus possible to lower the pour points andslightly increase the viscosity level compared to the unbranchedvariants.

In the case of the above-described diol esters, for example,1,6-hexanediol can also be prepared by branched diols from the group ofneopentyl glycol, 2,2,4-trimethyl-1,3-pentanediol and/or2-butyl-2-ethyl-1,3-propanediol.

H) Hydraulic Oils

Inventive hydraulic oils advantageously have at least 93% by weight of abase oil. For example, a hydraulic oil has the composition described inTable 1 below.

TABLE 1 Component Proportion [% by weight] Aminic antioxidants 0.30Phenolic antioxidants 0.50 Antiwear additives 0.80 Metal deactivators0.04 Corrosion inhibitors 0.20 Antifoams 0.02 Ester oil (dicarboxylic98.14 esters and/or diol esters)

L) Selected Diesters/Viscometric Properties

Table 2 below shows various viscometric properties of selected diesters.As can be inferred from the table, particularly the diesters having morethan 30 carbon atoms have relatively high viscosity levels (cf.Θ_(40° C.) values), which is particularly advantageous in the case ofuse as a hydraulic oil or lubricant. The values in the OECD 301 B/Fcolumn indicate the biodegradability according to the OECD test methodsknown per se. The UBA # column indicates the numbers assigned by theGerman Federal Environment Agency.

TABLE 2 Flash- NOACK Pour η_(40° C.) η_(100° C.) OECD 301 Base oil point[° C.] [%] VI point [° C.] [mm²/s] [mm²/s] UBA # B/F [%] AdipatesDiisodecyl adipate (C26) 235 15.5 148 −60 14.0 3.10 82 Di-n-tridecyladipate (C32) 5278 [16958-92-2] Diisotridecyl adipate (C32) 227 8-10 139−51 27.0 5.4 2362 92 [26401-35-4] Ditetradecyl adipate (C34) 75 34.3 5.1[26720-19-4] Azelates Didecyl azelate (C29) [2131-27-3] Diisodecylazelate (C29) 230 9.8 151 −65 18.1 4.3 3756 [28472-97-1] Diundecylazelate (C31) Didodecyl azelate (C33) [26719-99-3] Bis(2-hexyldecyl)azelate 278 160 −64 33.0 6.60 (C41) Di(isotridecyl) azelate 258 4.0 124−39 42.4 6.82 [27251-77-0] Ditridecyl azelate (C35) 243 145 −55 33.8 6.4[26719-40-4] Dodecanedioates Dioctyl dodecanedioate [42233-97-6]Diisooctyl dodecanedioate [85392-86-5] Di(iso-C9) dodecanedioate 6.0 184−25 23.2 5.28 4190 [63003-34-9] Di(C9) dodecanedioate 245 5.0 189 24.85.6 Di(isodecyl) dodecanedioate 266 3.5 161 −46 25.7 5.58 [63003-35-0]Di(isodecyl) dodecanedioate 4.3 162 −41 23.4 5.2 93 Ditridecyldodecanedioate (C38)[27742-10-5] Di(isotridecyl) 277 5.7 158 −57 42.07.5 4203 76 dodecanedioate (C38) [84731-63-5] Dicetyl dodecanedioate[42234-04-8] Diol esters Dodecanediol dipelargonate 7.4 182 −38 25.255.58 Hexanediol diisocaprilate 17.3 119 <−70 17.41 3.79 (C26) Hexanedioldiisomyristate (C34)

J) Comparative Tests with Selected Diesters

The unadditized ester base oils trimethylolpropane ester (TMP-C8/C10),diisotridecyl adipate (DITA), di(isotridecyl)dodecanedioate (C12D13,three samples), di(isotridecyl)decanedioate (C10D13, three samples) anddi(isotridecyl)nonanedioate (C9D13), and also the fully formulatedhydraulic oil “PANOLIN HLP Synth” based on DITA (obtainable fromPanolin, Switzerland) are compared in comparative tests hereinafter. Inaddition, the table also contains figures for a diester formed from adiol and two carboxylic acids, namely neopentyl glycol di(isostearate)(D5C18).

The lubricants used have the viscometric properties shown in Table 3.For the C12D13 esters and the C10D13 esters, three independentlyprepared samples were included in each case. For the C9D13 ester and forthe D5C18 ester, one sample was analyzed in each case. The“CCS_(−25° C.) [mPas]” and “CCS_(−20° C.) [mPas]” columns each containfigures for the “Cold Crank Simulator” according to the standard ASTMD5293 at −25° C. and −20° C. The HTHS_(150° C.) [mPas] column indicateswhat is called the “High-Temperature High-Shear Viscosity” (HTHS) atelevated temperature.

TABLE 3 Density Flash- NOACK Pour CCS_(−25° C.) CCS_(−20° C.) η_(40° C.)η_(100° C.) η_(150° C.) HTHS_(150° C.) Lubricant [g/cm³] point [° C.][%] VI point [° C.] [mPas] [mPas] [mm²/s] [mm²/s] [mmVs] [mPas] C12D130.9051 276 2.4 158 −48 3210 1910 40.47 7.573 3.453 2700 (1^(st) sample)C12D13 0.9020 277 4.3 147 −57 1700 42.0 7.5 (2^(nd) sample) C12D13 0.904261 2.9 156 −51 3230 41.2 7.6 (3^(rd) sample) C10D13 2.7 172 −52 35.57.2 (4^(th) sample) C10D13 250 4 150 −50 36.0 6.8 (5^(th) sample) C10D133.4 149 35.7 6.7 (6^(th) sample) C9D13 3.5 150 36.1 6.8 (7^(th) sample)D5C18 280 2.0 146 −44 46.0 8.0 (8^(th) sample) DITA 0.91 244 10.0 139−60 2646 1455 25 5 TMP-C8/10 0.94 235 3.6 140 −30 853 221 22 4.5 PANOLIN0.918 240 4.3 146 −57 4653 2780 47.0 8.10 HLP Synth

Table 4 contains ecotoxicological figures which are intended forguidance and are taken from safety data sheets. The “aquatic toxicity[mg/1]” column contains figures for the toxicity tests according to theknown test methods to OECD 201, 202 and 203.

TABLE 4 Aquatic toxicity [mg/l] OECD 301 OECD OECD OECD UBA LubricantB/F [%] 201 202 203 # C12D13 4203 (1^(st) sample) C12D13 76/93 880  >1000 4203 (2^(nd) sample) D5C18 85 >1000 >1000 >10 000 (8^(th)sample) DITA 87 >1000 >100 2362 TMP-C8/10 64-88 140 600 >10 000 5371PANOLIN 67-90 HLP Synth

In Table 3, a noticeable feature which is especially positive is thatthe NOACK vaporization (physical vaporization according to Noack, i.e.at 250° C. for 1 h) for the esters examined (samples 1-8) at 2.0-4.3%,even in the form of base oil, is at least much lower than for the esterbase oils trimethylolpropane esters (TMP-C8/C10, 3.6%) and diisotridecyladipate (DITA 10.0%). Trimethylolpropane esters (TMP-C8/C10) arecommercially available from various suppliers and have been used forcomparative purposes.

In addition, the NOACK values of the esters examined are also lower oridentical compared to the NOACK value of the commercially availablehydraulic oil “PANOLIN HLP Synth” (available from Panolin, Switzerland),which is a fully formulated hydraulic oil based on DITA. If the NOACKvalues of the esters examined are compared with “PANOLIN HLP Synth”, itcan be expected that the NOACK value for a hydraulic oil fullyformulated from an ester examined will be well below 2.0-4.3%. For theenvironment, this means less oil consumption, meaning introduction intothe environment, and, for the user, lower refilling costs, which lowersthe operating costs, and once again also benefits the environment in theform of resource protection.

Another advantage of the esters examined is the high flashpoint of up to280° C., which is about 40° above that of “PANOLIN HLP Synth”. This is adistinct safety gain and additionally opens up, through suitableadditization, the possibility of further raising the flashpoint into therange of low-flammability hydraulic fluids.

In viscometric terms, the C12D13 base oil is comparable to PANOLIN HLPSynth, i.e., for example, in the case of the kinematic viscosity at 40°C., without the addition of polymeric viscosity index improvers orthickeners. This results in better foaming characteristics, since theair bubbles are not stopped from rising by the macromolecules. Moreover,it can be assumed that the low-temperature viscosities of a polymer-freeformulation or one with reduced polymer content based on C12D13 will belower. This significantly improves lubrication at low temperatures, andlubrication film buildup is more rapid at all lubrication sites in theconstruction vehicle and the auxiliary equipment thereof, with lowerpump output (energy efficiency). This lowers wear in the tribologicalsystems (friction sites). This also applies to the other esters withshorter carboxylic acids examined.

The C12D13 base oil is classified by the committee for assessment ofwater-endangering substances at the German Federal Environment Agencyunder number 4203 in WGK 1 (slightly water-endangering, WGK=waterendangerment class) which is a good prerequisite for the formulation ofenvironmentally friendly hydraulic oils.

Overall, the esters examined exhibit higher viscosity indices, raisedviscosity levels, increased flashpoints, and also lower NOACKvaporizations compared to diisotridecyl adipate (DITA).

FIG. 1 shows the results of vibration-frictional wear tests (SRV, modelIII) with the five unadditized ester base oils diisotridecyl adipate(DITA), trimethylolpropane ester (TMP-C8/C10),di(isotridecyl)nonanedioate (C9D13), di(isotridecyl)dodecanedioate(C12D13) and di(isotridecyl)decanedioate (C10D13).

The tests were conducted according to standard ASTM D7421-08 (frettingload) at a typical operating temperature for hydraulic oils of +80° C.The frequency was 50 Hz with a stroke of 1 mm (in positive x direction)and 2 mm (in negative x direction). The standard force was increased by100 N every 2 minutes during the tests. It was found that the extensionof the chain length of the dicarboxylic acid also improves the frettingload-bearing capacity of the base oil. For C9D13, C10D13 and C12D13,values of greater than P_(0mean)=3938 MPa are achieved, since there isstill no occurrence of adhesive failure at 2000 N or after 40 minutes.

The C9D13 diesters and C12D13 diesters exceed the fretting load limitfor the trimethylolpropane ester (TMP-C8/C10) and, even as unadditizedbase oils, distinctly lower the mixed friction/boundary friction figureat high loads. What is remarkable in the case of these unadditized baseoils formed from C9D13 diesters and C12D13 diesters is the fact that themixed friction/boundary friction figure is virtually invariable withrespect to the rise in load in the test to ASTM D7421-08.

FIG. 2 a shows diagrams which illustrate the coefficient of friction (f)and the standard force (F_(N)) (top) and the stroke (dx) and thestandard force (F_(N)) (bottom) of diisotridecyl adipate in the positivex direction as a function of time.

FIG. 2 b correspondingly shows diagrams which describe the coefficientof friction (f) and the standard force (F_(N)) (top) and also the stroke(dx) and the standard force (F_(N)) (bottom) of diisotridecyl adipate inthe negative x direction as a function of time.

FIGS. 3 a,b show diagrams which describe the corresponding data fordi(isotridecyl) dodecanedioate (C12D13), while FIGS. 4 a,b analogouslyshow the diagrams for trimethylolpropane esters (TMP-C8/C10).

What is particularly remarkable is the high fretting load ofdi(isotridecyl) dodecanedioate (C12D13) of >1700 N after a time of about42 min (see, for example, FIG. 1). This is exceptionally high for a baseoil, particularly at this low viscosity level, and is not achieved byfully formulated lubricants without additional measures.

The esters examined, di(isotridecyl)nonanedioate (C9D13),di(isotridecyl)dodecanedioate (C12D13) and di(isotridecyl)decanedioate(C10D13), are to be used for lubricants marked with an ecolabel, which,based on the carbon content, consist of renewable raw materialspreferably to an extent of at least 25 mol %, further preferably atleast 50 mol %, even further preferably at least 60 mol %, especiallypreferably at least 70 mol %. For a new class of biolubes, it issufficient when at least 25 mol % of the overall formulation consists ofrenewable raw materials (RRM). Here too, the proportion is measured bymeans of radio carbon methods (ASTM D6866 or DIN EN 15440:2011-05).

This means that the ester C12D13 is already a biolube when only the acidcomponent (dodecanedioic acid, RRM content of 31.6%) originates fromrenewable raw materials. C10D13 (RRM content of 27.8%) and C9D13 (RRMcontent of 25.7%) also fulfill this criterion. In contrast, C6D13 (DITA,RRM content of 18.75%) alone cannot be regarded as a biolube. Alubricant based on DITA fulfills this specification if it containsfurther esters from renewable raw materials in small amounts whichcompensate the proportion of renewable raw materials can become.

1-45. (canceled)
 46. An ester oil, especially for production of ahydraulic oil and/or of a lubricant, comprising an esterificationproduct of at least one unbranched monoalcohol with at least onepolycarboxylic acid, characterized in that the unbranched monoalcoholand/or the polycarboxylic acid originates from renewable raw materials.47. The ester oil as claimed in claim 46, characterized in that thepolycarboxylic acid originates from renewable raw materials.
 48. Theester oil as claimed in claim 46, characterized in that thepolycarboxylic acid is saturated.
 49. The ester oil as claimed in claim46, characterized in that the polycarboxylic acid is unbranched.
 50. Theester oil as claimed in claim 46, characterized in that thepolycarboxylic acid is branched.
 51. The ester oil as claimed in claim46, characterized in that the polycarboxylic acid has 6-13 carbon atoms,preferably 8-13 carbon atoms.
 52. The ester oil as claimed in claim 46,characterized in that the polycarboxylic acid comprises a dicarboxylicacid.
 53. The ester oil as claimed in claim 52, characterized in thatthe dicarboxylic acid comprises adipic acid, trimethyladipic acid,suberic acid, azelaic acid, sebacic acid, dodecanedioic acid and/orbrassylic acid.
 54. The ester oil as claimed in claim 46, characterizedin that the at least one monoalcohol originates from renewable rawmaterials.
 55. The ester oil as claimed in claim 46, characterized inthat the at least one monoalcohol is saturated.
 56. The ester oil asclaimed in claim 46, characterized in that the at least one monoalcoholhas 6-24, preferably 8-16, carbon atoms, and the at least onemonoalcohol more preferably has 9, 11, 12, 14 and/or 16 carbon atoms.57. The ester oil as claimed in claim 46, characterized in that the atleast one monoalcohol is a fatty alcohol.
 58. The ester oil as claimedin claim 46, characterized in that the at least one monoalcoholcomprises 1-nonanol, n-undecanol, 1-dodecanol, 1-tetradecanol and/orcetyl alcohol.
 59. The ester oil as claimed in claim 46, characterizedin that the esterification product, based on the carbon content, isformed to an extent of at least 50 mol %, preferably at least 60 mol %,even further preferably at least 70 mol %, from renewable raw materials.60. The ester oil as claimed in claim 46, characterized in that amolecular weight of the esterification product is at least 400 g/mol,especially 550 g/mol.
 61. The ester oil as claimed in claim 46,characterized in that the esterification product has at least 30 carbonatoms and/or at most 50 carbon atoms.
 62. The use of an ester oil asclaimed in claim 46 as a lubricant and/or hydraulic oil.
 63. A lubricantand/or hydraulic oil comprising an ester oil as claimed in claim
 46. 64.The lubricant and/or hydraulic oil as claimed in claim 63, characterizedin that the proportion of ester oil is at least 50% by weight,preferably at least 75% by weight, further preferably at least 90% byweight, of the total weight of the lubricant and/or hydraulic oil. 65.The lubricant and/or hydraulic oil as claimed in claim 63, characterizedin that additives are present, the additives present being antioxidants,antiwear additives, metal deactivators, corrosion inhibitors and/orantifoams.
 66. A process for preparing an ester oil, especially for usein a hydraulic oil and/or a lubricant, by reacting an unbranchedmonoalcohol with a polycarboxylic acid to give an ester oil,characterized in that the unbranched monoalcohol and/or thepolycarboxylic acid originate from renewable raw materials.
 67. Theprocess as claimed in claim 66, characterized in that the alcoholsand/or carboxylic acids are prepared from fatty acids from renewable rawmaterials.
 68. An ester oil, especially for production of a hydraulicoil and/or of a lubricant, comprising an esterification product of atleast one branched monoalcohol with at least one polycarboxylic acid,characterized in that the branched monoalcohol and/or the polycarboxylicacid originates from renewable raw materials and the at least onebranched monoalcohol has a terminal iso branch.
 69. The ester oil asclaimed in claim 68, characterized in that the polycarboxylic acidoriginates from renewable raw materials.
 70. The ester oil as claimed inclaim 68, characterized in that the polycarboxylic acid is saturated.71. The ester oil as claimed in claim 68, characterized in that thepolycarboxylic acid is unbranched.
 72. The ester oil as claimed in claim68, characterized in that the polycarboxylic acid is branched.
 73. Theester oil as claimed in claim 68, characterized in that thepolycarboxylic acid has 6-13 carbon atoms, preferably 8-13 carbon atoms.74. The ester oil as claimed in claim 68, characterized in that thepolycarboxylic acid comprises a dicarboxylic acid.
 75. The ester oil asclaimed in claim 74, characterized in that the dicarboxylic acidcomprises adipic acid, trimethyladipic acid, suberic acid, azelaic acid,sebacic acid, dodecanedioic acid and/or brassylic acid.
 76. The esteroil as claimed in claim 68, characterized in that the at least onemonoalcohol originates from renewable raw materials.
 77. The ester oilas claimed in claim 68, characterized in that the at least onemonoalcohol is saturated.
 78. The ester oil as claimed in claim 68,characterized in that the at least one monoalcohol has 6-24, preferably8-16, carbon atoms, and the at least one monoalcohol more preferably has9, 11, 12, 14 and/or 16 carbon atoms.
 79. The ester oil as claimed inclaim 68, characterized in that the at least one monoalcohol is a fattyalcohol.
 80. The ester oil as claimed in claim 68, characterized in thatthe at least one monoalcohol comprises methyltetradecanol.
 81. The esteroil as claimed in claim 68, characterized in that the esterificationproduct, based on the carbon content, is formed to an extent of at least50 mol %, preferably at least 60 mol %, even further preferably at least70 mol %, from renewable raw materials.
 82. The ester oil as claimed inclaim 68, characterized in that a molecular weight of the esterificationproduct is at least 400 g/mol, especially 550 g/mol.
 83. The ester oilas claimed in claim 68, characterized in that the esterification producthas at least 30 carbon atoms and/or at most 50 carbon atoms.
 84. The useof an ester oil as claimed in claim 68 as a lubricant and/or hydraulicoil.
 85. A lubricant and/or hydraulic oil comprising an ester oil asclaimed in claim
 68. 86. The lubricant and/or hydraulic oil as claimedin claim 85, characterized in that the proportion of ester oil is atleast 50% by weight, preferably at least 75% by weight, furtherpreferably at least 90% by weight, of the total weight of the lubricantand/or hydraulic oil.
 87. The lubricant and/or hydraulic oil as claimedin claim 85, characterized in that additives are present, the additivespresent being antioxidants, antiwear additives, metal deactivators,corrosion inhibitors and/or antifoams.
 88. A process for preparing anester oil, especially for use in a hydraulic oil and/or a lubricant, byreacting a branched monoalcohol with a polycarboxylic acid to give anester oil, characterized in that the branched monoalcohol and/or thepolycarboxylic acid originate from renewable raw materials and the atleast one branched monoalcohol has a terminal iso branch.
 89. Theprocess as claimed in claim 88, characterized in that the alcoholsand/or carboxylic acids are prepared from fatty acids from renewable rawmaterials.